eric_b Key Veteran Location: Denver, CO, USA
| The cause was not 100% certain, but likely due to power/payload overloading which caused shaft flex in the turbine gearbox. This caused the power turbine wheel to strike the housing, tearing off the blade and bending several others, also damaging a stator downstream. The housing contained the debris, it was just dented. It also destroyed the gearbox bearings, and gearing. The turbine (gas generator) was undamaged. The vibration of the unbalanced turbine wheel (at 65,000 rpm!) was serious, as was the noise, but luckily I was able to land immediately and shut it down before anything else was damaged. The turbine manufacturer has re-engineered the second stage gearbox for heavy duty operations, and it is now working perfectly. |